Fix various typescript inconsistencies (#319)

* Add ref types to SnackbarProvider

* Rename SnackbarContent callback type

* Better name for SnackbarContent props

src/SnackbarContent/SnackbarContent.tsx

@@ -14,9 +14,9 @@ const styles = (theme: Theme) => createStyles({
     }
 });
 
-export interface SnackbarContent extends WithStyles<typeof styles>, React.HTMLAttributes<HTMLDivElement> { }
+interface SnackbarContentProps extends WithStyles<typeof styles>, React.HTMLAttributes<HTMLDivElement> { }
 
-const SnackbarContent: React.FC<SnackbarContent> = forwardRef<HTMLDivElement, SnackbarContent>(({ classes, className, ...props }, ref) => (
+const SnackbarContent = forwardRef<HTMLDivElement, SnackbarContentProps>(({ classes, className, ...props }, ref) => (
     <div ref={ref} className={clsx(classes.root, className)}  {...props} />
 ))
 

src/index.d.ts

@@ -19,7 +19,7 @@ export type CloseReason = 'timeout' | 'clickaway' | 'maxsnack' | 'instructed';
 
 export type SnackbarMessage = string | React.ReactNode;
 export type SnackbarAction = React.ReactNode | ((key: SnackbarKey) => React.ReactNode);
-export type SnackbarContent = React.ReactNode | ((key: SnackbarKey, message: SnackbarMessage) => React.ReactNode);
+export type SnackbarContentCallback = React.ReactNode | ((key: SnackbarKey, message: SnackbarMessage) => React.ReactNode);
 
 
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -192,7 +192,7 @@ export interface SharedProps extends Omit<SnackbarProps, 'classes'>, Partial<Tra
      * Replace the snackbar. Callback used for displaying entirely customized snackbar.
      * @param {string|number} key key of a snackbar
      */
-    content?: SnackbarContent;
+    content?: SnackbarContentCallback;
     /**
      * Callback used for getting action(s). actions are mostly buttons displayed in Snackbar.
      * @param {string|number} key key of a snackbar
@@ -253,9 +253,16 @@ export interface SnackbarProviderProps extends SharedProps {
      * Little icon that is displayed at left corner of a snackbar.
      */
     iconVariant?: Partial<IconVariant>;
+    /**
+     * SnackbarProvider's ref
+     */
+    ref?: React.Ref<SnackbarProvider>;
 }
 
-export const SnackbarProvider: React.ComponentType<SnackbarProviderProps>;
+export class SnackbarProvider extends React.Component<SnackbarProviderProps> {
+    enqueueSnackbar: ProviderContext['enqueueSnackbar'];
+    closeSnackbar: ProviderContext['closeSnackbar'];
+}
 
 export interface ProviderContext {
     enqueueSnackbar: (message: SnackbarMessage, options?: OptionsObject) => SnackbarKey;